External validation of predictive models of sexual, urinary, bowel and hormonal function after surgery in prostate cancer subjects

Matthew A. Borg, Michael E. O’Callaghan, Kim L. Moretti, Andrew D. Vincent

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Background: In 2020, a research group published five linear longitudinal models, predict Expanded Prostate Cancer Index Composite-26 (EPIC-26) scores post-treatment for radical prostatectomy, external beam radiotherapy and active surveillance collectively in US patients with localized prostate cancer. Methods: Our study externally validates the five prediction models for patient reported outcomes post-surgery for localised prostate cancer. The models’ calibration, fit, variance explained and discrimination (concordance-indices) were assessed. Two Australian validation cohorts 1 and 2 years post-prostatectomy were constructed, consisting of 669 and 439 subjects, respectively (750 in total). Patient reported function in five domains post-prostatectomy: sexual, bowel, hormonal, urinary incontinence and other urinary dysfunction (irritation/obstruction). Domain function was assessed using the EPIC-26 questionnaire. Results: 1 year post-surgery, R2 was highest for the sexual domain (35%, SD = 0.02), lower for the bowel (21%, SD = 0.03) and hormone (15%, SD = 0.03) domains, and close to zero for urinary incontinence (1%, SD = 0.01) and irritation/obstruction (− 5%, SD = 0.04). Calibration slopes for these five models were 1.04 (SD = 0.04), 0.84 (SD = 0.06), 0.85 (SD = 0.06), 1.16 (SD = 0.13) and 0.45 (SD = 0.04), respectively. Calibration-in-the-large values were − 2.2 (SD = 0.6), 2.1 (SD = 0.01), 5.1 (SD = 0.1), 9.6 (SD = 0.9) and 4.0 (SD = 0.2), respectively. Concordance-indices were 0.73, 0.70, 0.70, 0.58 and 0.62, respectively (all had SD = 0.01). Mean absolute error and root mean square error were similar across the validation and development cohorts. The validation measures were largely similar at 2 years post-surgery. Conclusions: The sexual, bowel and hormone domain models validated well and show promise for accurately predicting patient reported outcomes in a non-US surgical population. The urinary domain models validated poorly and may require recalibration or revision.

Original languageEnglish
Article number2
Number of pages8
JournalBMC Urology
Issue number1
Publication statusPublished - Dec 2024


  • External validation
  • Patient-reported outcomes
  • Prostate cancer
  • Prostatectomy


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